Over debit

In Dec 2014 I changed jobs and contacted the home loan department to inform them of change of payment dated from the15th to the 27th of the month. I was told I can not do the change telephonically and must write a letter and email it to home loans. I did as requested only to have the email rejected as STD BANK email wasn't working. After numerous call I was told to fax the letter which I did and of co****, was told the fax wasn't received. I paid my bond installment via EFT as stated on my letter. Jan 2015 I was contacted as my payment was not received on the 15th. After explaining the situation the agent said he would change it on the system over the phone! I again paid via EFT as I said and paid again in Feb 2015 on the 27th as I had arranged, only get a debit order deduction on the 1 Mar which has now put my cheque acc in negative balance. I have tried to rectify the debit but as usual haven't had any success with home loan call center. this is unacceptable and will have to now wait for my money to be reversed!!!!!